Hello Algeee,
It is always difficult to give precise repair advice when it comes to water ingress issues, as when you find evidence of ingress, such as damp patches or water as in your case, the actual fault allowing the water in could be some distance from the point you actually see the evidence.
However if you are seeing running water, then there is a probably a significant failure, and it needs to be inspected and sorted quickly to avoid accelerated deterioration.
I'm sure you can understand that trying to resolve the source of a leak through a forum will never be as reliable because we can't inspect the caravan first hand. I suspect you may need to get it checked by a professional.
However you problem is very likely to be a failed seal and the solution is to get them re sealed, which usually means removing the rail(s), cleaning off any remaining residue of old sealing compounds and using new compound to rebed the rail.